dart extending list
import 'dart:collection';
class MyCustomList<E> extends ListBase<E> {
final List<E> l = [];
set length(int newLength) {
l.length = newLength;
}
int get length => l.length;
E operator [](int index) => l[index];
void operator []=(int index, E value) {
l[index] = value;
}
}